[GHC] #8281: The impossible happened: primRepToFFIType

[GHC]

#8281: The impossible happened: primRepToFFIType
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        Reporter:  tibbe               |            Owner:
            Type:  bug                 |           Status:  new
        Priority:  normal              |        Milestone:
       Component:  Compiler            |          Version:  7.6.2
      Resolution:                      |         Keywords:
Operating System:  Unknown/Multiple    |     Architecture:
 Type of failure:  Compile-time crash  |  Unknown/Multiple
       Test Case:                      |       Difficulty:  Unknown
        Blocking:                      |       Blocked By:
                                       |  Related Tickets:
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Comment (by errge):

 I met this today and came up with the following temporary workaround:
 {{{#!haskell
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE UnliftedFFITypes #-}
 {-# LANGUAGE ForeignFunctionInterface #-}

 import Control.Concurrent
 import GHC.Conc.Sync
 import Foreign.C
 import GHC.Base

 foreign import ccall unsafe "rts_getThreadId" getThreadId# :: Addr# ->
 CInt

 getThreadId :: ThreadId -> CInt
 {-# INLINE getThreadId #-}
 getThreadId (ThreadId tid) = getThreadId# (unsafeCoerce# tid)

 threadId :: IO Int
 {-# INLINE threadId #-}
 threadId = do
   mtid <- myThreadId
   return $ fromIntegral $ getThreadId mtid

 main = do
   print =<< threadId
   forkIO $ print =<< threadId
   threadDelay 10000
 }}}
 Seems to work with ghci and 32/64-bit compiled and 32/64-bit optimized
 code.

 Total noob in this area, please tell me if this is dangerous somehow.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8281#comment:4>
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